1. Field of the Invention
This invention relates to PSK modem phase locked loops and in particular to phase locked loops employing field effect transistors and switched capacitor filters.
2. Description of the Prior Art
Discrete component phase locked loops are well known in the prior art. Integrated circuit phase locked loops are also well known.
The problem encountered in the model of this invention is the inability of the integrator to react quickly to cause the loop to lock. In the prior art, expensive and very fast operational amplifiers were utilized in the integrator circuits.
According to this invention, an ordinary integratory circuit of moderate speed is used in conjunction with a low pass filter whose output, summed with the output of the integrator, permits high speed operation.